This invention relates to a channel division control equipment of the ISDN primary rate interface circuit when a call is received by the private automatic branch exchange (PABX) accommodating the ISDN primary rate interface circuit.
In the past, in a PABX accommodating multiple analog circuits and using multiple telephone numbers where operation is made by allocating a circuit and a telephone number to a certain extension group, the above operation has been executed by acquiring the circuit allocated by the control of the PABX when making a call from an extension number, and by allocating the receiving circuit for each telephone number by the control of the switchboard at the telephone office when receiving a call.
Therefore, in this type of equipment, the ISDN primary rate interface circuit had to be handled as a group when accommodating the ISDN primary rate interface circuit, and a circuit could not be divided for a certain extension group and handled independently. For example, suppose there are three groups, A, B and C, as the communication channels and the calling parties, and suppose they jointly use 23 channels, if group A occupies many channels, there was a problem that B and C could not use those channels, thus channel availability was restricted by the use by group A, a third party, which was inefficient.
In a PABX accommodating the ISDN primary rate interface circuit and using multiple telephone numbers, in order not to be restricted in use by the use by other group(s), the communication channels need to be preallocated to the extension groups. And, operation by allocating the communication channels of the ISDN primary rate interface circuit to the extension groups can be achieved by using the communication channels allocated by the control of the PABX when making a call from an extension number.
When receiving a call, however, the current method is such that an available channel is designated for response after the destination number information element, including the channel identification element, is received when a call is received from the switchboard office. As a result, a call cannot be received by designating a communication channel of the ISDN primary rate interface circuit for each telephone number, and therefore, a problem exists that a method of preallocating the communication channels to each extension group by dividing the communication channels of the ISDN primary rate interface circuit cannot be accomplished. Furthermore, even in the case where it has been enabled for a call to be received by designating communication channel of the ISDN primary rate interface circuit, there was a problem that allocation of the communication channels could not be changed easily because a change of the communication channel allocation required a data change at the office switchboard.
This invention is made in consideration of the above problems, and it is intended to provide a control equipment for a PABX which enables easy change of the communication channel allocation of the ISDN primary rate interface circuit as well as enabling an operation by allocating the communication channels of the ISDN primary rate interface circuit to the extension groups.
In order to solve above problems, the channel division control equipment of the ISDN primary rate interface circuit under this invention consists of a memory unit, a switch control means which selects a communication channel when making a call from an extension number, and a switch control means which selects a communication channel when receiving a call from the ISDN primary rate interface circuit. The memory unit stores an extension number/extension group cross-reference table where the extension numbers and the extension group numbers are related to each other, a communication channel/channel group cross-reference is table where the communication channels of the ISDN primary rate interface circuit and the channel group numbers are related to each other, a destination number/channel group cross-reference table where the destination numbers and the channel groups are related to each other, a global channel group cross-reference table where the control channel numbers and the channel group numbers are related to each other when the destination number information element informed from the ISDN primary rate interface circuit and the channel group number do not relate to each other and when the destination number information element is not informed, and an extension group/channel group cross-reference table where the extension group numbers and the channel group numbers are related to each other.